depends on what you define as occasional commute, i am doing 17ish each way and it does wear things out! You don't need to spend a fortune, but be aware that better shifters are a bit more durable. The more you can spend the better.

I got a Giant Defy 1 back in October and have been shocked about how much I've used it since. The mountain bike has hardly been out of the garage!

For me paying the extra money for the 1 is worth it. The 105 groupset works so well and is very crisp, the brakes are excellent and it just rides so well. Comfy, confidence inspiring handling and plenty quick enough for me. Sure, the wheels could be lighter, but its a great first road bike for me & that's the only upgrade I can think of that could be worthwhile.